Automatic keystone correction system and method

• US 7,808,513 B1
• Filed: 04/26/2004
• Issued: 10/05/2010
• Est. Priority Date: 01/28/2003
• Status: Active Grant

• Current Assignee: Pixelworks Semiconductor Technology Company Limited
• Original Assignee: Pixelworks Incorporated
• Inventors: Teng, Tianbing Brian
• Primary Examiner(s): Lefkowitz; Sumati
• Assistant Examiner(s): Pham; Tammy
• Application Number:
  US10/832,488
• Time in Patent Office: 2,353 Days
• Field of Search: 345/649, 345646- 8, 345/204, 348745- 6, 722/715
• US Class Current: 345/647
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 27/58 Baseboards, masking frames, or other holders for the sensitive material G03B27/53 takes precedence ; for electrophotographic copiers G03G15/65
• CPC Class Codes: G03B 5/04 Vertical adjustment of lens; Rising fronts
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/028 by changing the viewing angle properties, e.g. widening the viewing angle, adapting the viewing angle to the view direction
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2320/08 Arrangements within a display terminal for setting, manually or automatically, display parameters of the display terminal
• CPC Class Codes: G09G 2370/04 Exchange of auxiliary data, i.e. other than image data, between monitor and graphics controller
• CPC Class Codes: G09G 3/001 using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G09G 3/002 to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 9/31 Projection devices for colour picture display , e.g. using electronic spatial light modulators [ESLM]
• CPC Class Codes: H04N 9/3185 Geometric adjustment, e.g. keystone or convergence optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

The invention relates to an automatic keystone correction system and method. The system includes an interface to display a pattern on a projection surface and a controller to distort image data responsive to the pattern. The pattern includes a plurality of polygons, each with a predetermined shape. Each polygon corresponds to a particular system rotation angle. The controller distorts the image data responsive to the rotation angle. A user interacts with the interface to identify a particular polygon that, when projected on a projection surface, has a predetermined shape.

Claims

1. A system, comprising:

a projector including an interface configured to;

display a pattern set on a projection surface separate from the projector, where the pattern set comprises a plurality of partially overlapping polygons and each polygon is different from the remaining polygons in one or more of shape and rotation such that each of the plurality of polygons corresponds to a different combination of horizontal rotation angle and vertical tilt angle of the projector with respect to the projection surface; and

receive a selection from a user of a selected polygon in the pattern set, where the selected polygon comprises an entire polygon and represents a minimum amount of keystone distortion as compared to the remaining polygons in the pattern set; and

a controller in the projector to distort image data dependent upon which of the plurality of polygons is selected by the user and the horizontal rotation angle and vertical tilt angle corresponding to the selected polygon, wherein the controller is configured to distort the image data by vertically scaling the image data using the function f₂, where;

2. The system of claim 1 where each of the plurality of polygons has a predetermined shape corresponding to the different combination of horizontal rotation angle and vertical tilt angle of the projector with respect to the projection surface.

3. The system of claim 1 where the selected polygon has a predetermined shape as viewed by the user when projected on the projection surface.

4. The system of claim 3 where the predetermined shape comprises a rectangle with four angles of approximately 90 degrees each.

5. The system of claim 1 where the controller distorts the image data prior to its projection on the projection surface.

6. The system of claim 1 where each of the plurality of polygons has a corner and where the corner of each of the plurality of polygons has a different angle than the corners of the remaining polygons.

7. The system of claim 1 further comprising a memory to store a table comprising the correspondence of each of the plurality of polygons to the different combination of horizontal rotation angle and vertical tilt angle.

8. The system of claim 1, wherein the controller is configured to distort the image data by horizontally scaling the image data using the function f₃, where:

9. A method for keystone correction, comprising:

receiving a request from a user to project a calibration pattern on a projection surface separate from a projector;

projecting a plurality of substantially overlapping polygons from the projector onto the projection surface, where each polygon is different from the remaining polygons in one or more of shape and rotation such that each of the plurality of polygons corresponds to a different combination of horizontal rotation angle and vertical tilt angle of the projector with respect to the projection surface;

receiving a selection from a user of one of the projected polygons, where the selected polygon comprises an entire polygon, where the selected polygon has a rectangular shape, where non-selected polygons are one or more of shapes other than a rectangle and rectangular shapes rotated with respect to the selected polygon, and where the non-selected polygons have a greater amount of keystone distortion than the selected polygon; and

distorting image data prior to its projection on the projection surface based upon which of the plurality of polygons is selected by the user and the horizontal rotation angle and vertical tilt angle corresponding to the selected polygon, wherein distorting the image data comprises;

vertically scaling the image data responsive to at least a set of vertical offset registers and a set of vertical registers, wherein the set of vertical offset registers comprises a column even register (YE), a column odd register (YO), and a column increment (1^st order term) register (YI), and wherein the set of vertical registers comprises a line position register (VDN), an increment per line (1^st order term) register (VDNI), and an increment per column register (VDNPI); and

horizontally scaling the vertically scaled image data responsive to at least a set of horizontal offset registers and a set of horizontal registers, wherein the set of horizontal offset registers comprises a row even register (XE), a row odd register (XO), and a row increment (1^st order term) register (XI), and wherein the set of horizontal registers comprises a row position register (HDN), an increment per line (1^st order term) register (HDNI), an increment per line (2^nd order term) register (HDNII), an increment per column (1^st order term) register (HDNPI), and an increment per column (2^nd order term) register (HDNPII).

10. The method of claim 9 comprising associating each of the polygons with the corresponding combination of horizontal rotation angle and vertical tilt angle.

11. The method of claim 9 where projecting the plurality of polygons includes projecting a plurality of polygons, each having a predetermined shape corresponding to the different combination of horizontal rotation angle and vertical tilt angle of the projector with respect to the projection surface.

12. The method of claim 9 where distorting image data comprises adjusting horizontal and vertical image data to compensate for the horizontal rotation angle and vertical tilt angle corresponding to the selected polygon.

13. A keystone apparatus, comprising:

means for projecting a pattern means on a projection surface means, where the pattern means comprises a plurality of substantially overlapping polygons and each polygon is different from the remaining polygons in one or more of shape and rotation such that each of the plurality of polygons corresponds to a different combination of horizontal rotation angle and vertical tilt angle of the projector with respect to the projection surface;

means for receiving a selection of a selected one of the polygons from a user;

means for generating vertically scaled data by vertically scaling image data using a first polynomial function f₂, where;

14. The keystone apparatus of claim 13 where each of the plurality of polygons has a predetermined shape.

15. The keystone apparatus of claim 13 where each of the plurality of polygons projects on a projection surface having a predetermined shape.

16. The keystone apparatus of claim 15 where the predetermined shape is rectangular.

17. The keystone apparatus of claim 13 where the controller means distorts the image data prior to its projection on the projection surface means.